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Visual evoked potential stimulus intensity modulation and sensation seeking in thrill-seekers
Person. individ. Diff. Vol. 14, No. 3, pp. 455463, Printed in Great Britain. All rights reserved
0191-8869/93 $6.00+ 0.00 Copyright 0 1993Pergamon Press Ltd
1993
VISUAL EVOKED POTENTIAL STIMULUS INTENSITY MODULATION AND SENSATION SEEKING IN THRILL-SEEKERS JANET L. BLENNER College of Health and Human Services, San Diego State University, (Received
IO November
San Diego, CA 92182-0254,
1991; received for publication
U.S.A
30 June 1993)
Summary-Visual
evoked potentials (VEPs) to stimuli of four intensities of 4, 18, 75, and 320 footcandles (ft-c) were recorded and Zuckerman’s sensation seeking scale (SSS) was administered to 59 thrill-seekers and 59 non-thrill-seeker control subjects. The thrill-seekers were a heterogeneous group composed of skydivers, hang-gliders, rock climbers, ultralight flyers, scuba divers, motorcycle racers, and ocean kayakers. Amplitude/intensity function slopes were computed PIN1 and NIP2 components on lead Cz. Thrill-seekers had significantly lower slope on NIP2 but were not significantly different from controls on PIN 1.The only significant correlation between VEP and SSS was for the disinhibition scale (Dis) on PIN 1 (0.29). Thrill-seekers were significantly higher than controls on all of the SSS subscales. Thrill-seekers’ highest mean score was reported on the thrill and adventure seeking scale (TAS). TAS also discriminated the best between the groups. Female thrill-seekers less than 30 years old had mean scores higher than their male counterparts on all SSS scales except Dis.
INTRODUCTION
Origins of stimulus intensity modulation can be found in the work of Eysenck (1953, who developed the notion that extraverts show more satiation effects than introverts. Petrie (1960) extended this notion into a theory of perceptual reactance. Petrie (1967) devised the Kinesthetic Figural Aftereffect (KFA), a psychophysical measure of the construct, where Ss judge the size of a stimulation block. Central nervous system (CNS) augmenters tend to subjectively increase in poststimulation block-size judgment while CNS reducers subjectively decrease in their judgment size. Buchsbaum and Silverman (1968) developed a visual evoked potential (VEP) procedure as a measure of the construct and coined the term stimulus intensity modulation. They demonstrated correlations between KFA and VEP measures. The theory of stimulus intensity modulation presupposes that each person has a subjective tendency to react to various intensities of stimuli that is directly related to the ability of the person’s nervous system to modulate responses. Essentially, individuals differ in the way they react to various intensities of environmental stimuli. When light intensity is viewed from dim to bright, the VEP amplitude response may increase or decrease at different rates. Persons are classified as either cortical augmenters, those in whom the VEP amplitude response increases, or cortical reducers, those in whom the response to the same series of increasing stimulus intensities decreases (Silverman, Buchsbaum & Henkin, 1969; Buchsbaum & Pfefferbaum, 1971). The traditional Buchsbaum (1976) procedure for measuring stimulus intensity modulation commonly uses visual stimuli and measures at the slope of the vertex PlO(rN120 amplitude. Positive slopes define the augmenting end of the continuum, and less positive and even negative slopes define the reducing end. Zuckerman’s sensation seeking is based on constructs of optimal levels of stimulation devoted to maintaining optimal levels of arousal. Sensation seeking is described by Zuckerman (1979) as a trait reflected in the “need for varied, novel, and complex sensations and experiences and the willingness to undertake physical and social risks for the sake of such experiences” (p. 10). Zuckerman, Kolin, Price and Zoob (1964) devised the original sensation seeking scale (SSS). According to the measure, individuals high in sensation seeking are thought to respond as though stimuli are less intense and tend to prefer experiences that are intense, unusual or unpredictable or that have an edge of danger (Zuckerman, 1984a). They have an aversion to routine and are open to changes from their usual environment if the changes facilitate new experiences (Zuckerman, 455
456
JANETL. BLENNER
Murtaugh & Siegel, 1974). Zuckerman (1983) contends that sensation seeking is relevant to sports involving high levels of personal risk and novel sensations. He suggests that skydiving and scuba diving would be some of the sports tailored to people with a high sensation seeking trait. Zuckerman (1979) states, “It would not be surprising to find that persons who actually engage in these (high-risk sport) activities . . . score high on SSS” (p. 206). Thrill-seekers engage in sports in which the risk of physical injury and even death to participants is high. Most studies of thrill-seekers have focused on the S’s personality and motivation to participate in these sports. Some researchers have administered the SSS to thrill-seekers and to persons in high-risk occupations. Hymbaugh and Garrett (1974) gave the original SSS to skydivers and matched controls and found that the skydivers scored higher than the controls on the total (Tot) score. In a study by Straub (1982), auto racers had the highest scores on the SSS form V, followed by hang gliders, and last were bowlers. The experience seeking (ES) scale followed by boredom susceptibility (BS) and thrill and adventure seeking (TAS) differentiated the groups the most. Kusysyzn, Steinberg and Elliot (1973) compared a mixed group of men involved in risk-taking occupations and sports, including firemen, riot squad policemen, race car drivers, skydivers and snowmobilers, with a control group and found those involved in risk taking scored higher on the General (Gen) and TAS scales of the SSS form IV. Bacon (1974) administered the SSS form IV to divers and firemen who are often engaged in high-risk activity and to control Ss. Both high-risk groups were significantly higher than the control group on the Gen, disinhibition (Dis) and BS scales. However, only the divers were higher on the TAS scale. Neither high-risk group was significantly higher than the control group on the ES scale. Connolly (1981) studied recreational skiers, ski instructors and non-skiers and found that of the three groups, ski instructors had the highest scores on the total SSS, ES and TAS scales of the SSS form V. Bouter, Knipschild, Feij and Volovics (1988) administered a Dutch version of the SSS to skiers and found them to have higher TAS scores than non-skiers. Cronin (1991) found that mountain climbers scored higher on the Tot, ES and TAS scales of the SSS form V than control Ss. The relationship of stimulus intensity modulation and sensation seeking has been viewed from two theoretical perspectives. From Petrie’s (1960) perspective, reducers are stimulus deprived and should seek out complex and intense stimulus situations. Augmenters amplify sensory experience and should prefer low stimuli and are likely to seek out and respond favorably to quiet and dull stimulus situations. This perspective has been upheld by KFA studies (e.g. Petrie, Collins & Solomon, 1958; Sales, 1971, 1972). Zuckerman (e.g. Zuckerman, 1979; Zuckerman, Buchsbaum & Murphy, 1980) take the opposite position: that evoked potential augmenters increase afferent stimuli and seek sensations to satisfy a high optimal arousal level and reducers decrease stimulation and avoid sensations to satisfy a low optimal arousal level. The differences between the two positions have been attributed to semantics with Petrie defining augmenting-reducing as a subjective experience, and Buchsbaum and Zuckerman defining it as a physiological response (Davis, Cowles & Kohn, 1983). Essentially, KFA augmenters are evoked potential reducers. In spite of this explanation, evoked potential studies alone have had conflicting findings. (For a review and in depth discussion of all the evoked potential studies with SSS, see Zuckerman, 1990.) Using VEP procedures, Haier, Robinson, Braden and Williams (1984) found reducing related to high scores on all the SSS scales except Dis which did not differentiate augmenters from reducers. Four studies (Sternberg, Rosen & Risberg, 1988; von Knorring, 1981; Zuckerman, Murtaugh & Siegel, 1974; Zuckerman, Simons & Como, 1988) found VEP augmenting related to the Dis scale. Lukas (1987) found VEP augmentation related to the Tot scale while Coursey, Buchsbaum and Frankel (1975) found this relationship with the Gen scale. In addition, two studies (Hall, 1970; Lukas & Siegel, 1977) found a relationship Rappaport, Hopkins, Griffin & Silverman, between VEP augmenting and behavioral ratings of sensation seeking in cats. Significant findings were also found for some auditory evoked potential (AEP) studies with SSS. Zuckerman et al. (1988) found a relationship between AEP augmenting with Dis while von Knorring (1981) found this relationship with both Dis and Gen scales. Coursey et al. (1975) found a significant relationship between Gen and AEP augmenting in a study of insomnia. In attention conditions, Lukas and Mullins (1983) did not find a relationship between any of the SSS scales
VEP and sensation
seeking
in thrill-seekers
457
in their initial study, however subsequent studies found an augmenting relationship with Dis and Tot (Mullins & Lukas, 1984) and ES, BS and Tot (Lukas & Mullins, 1985). Orlebeke, Kok and Zeillemaker (1989) found a relationship between low augmenting and high Dis in both passive and active conditions. It must be noted that variance existed between the aforementioned studies as to their procedures, conditions, and components used in the analysis. Haier et al. (1984) have criticized these findings as to their deviation from the customary Buchsbaum (1976) VEP procedure which they claim contribute to problems in defining augmenting and reducing. The problem is perceived as being the variance among laboratories as to their use of different intensities, durations, and stimulation procedures while claiming to measure the same phenomenon. Discussion of these paradigm differences can be found in Haier (1984) and Zuckerman (1984b). Only Haier et al. (1984) used the customary Buchsbaum (1976) VEP apparatus and procedure. The aim of this present study is to relate VEP (using the customary Buchsbaum apparatus and procedure) and SSS to individual differences in sensation seeking behavior rather than only personality SSS scale scores and answer the following questions: (1) Do behaviorally high sensation seekers (thrill-seekers) have significantly greater VEP augmentation or reduction than non-thrillseeking control Ss? (2) Is sensation seeking as measured by the SSS related to VEP augmentation or reduction? (3) Do behaviorally high sensation seekers (thrill-seekers) score significantly higher than non-thrill-seeking control Ss on the SSS dimensions. 7 This study will also contribute information to the construct validity of the SSS and meet Zuckerman’s (1983) call for studies relating sensation seeking to risk-taking sports.
METHOD Subjects One hundred and eighteen volunteer Ss from Southern California completed the testing as described below. Of that sample, 59 were thrill-seekers (male = 49; female = 10). The remaining 59 were non-thrill-seeker control Ss who were selected to balance with the thrill-seeking group with respect to age (under and over 30 years) and gender. Thrill-seekers were recruited by addressing thrill-seeking clubs and organizations and placing local newspaper ads and flyers in adventure equipment and travel stores in San Diego, California. Thrill-seeker Ss needed to meet the following criteria to be included in the study: participation in a high-risk sport on a regular, ongoing basis for a minimum of 1 year and no previous history of major visual or neurological problems. Non-thrill-seeker control Ss were recruited from both undergraduate and graduate students and staff from local universities. They were not currently or previously engaged in high-risk sports. They were also screened by medical history for any neurological or visual problems. Thrill-seeking Ss represented the following groups: skydivers (n = 20) hang-gliders (n = lo), rock climbers (n = 14); ultralight flyers (n = 6); high-risk scuba divers (n = 4); motorcycle racers (n = 2); and ocean kayakers (n = 3). Of the female thrill-seekers (n = 10) there were 5 skydivers, 1 hang glider, 1 rock climber, 2 scuba divers and 1 ocean kayaker. Thrill-seekers’ age range was 19-59 years (mean = 28.9; SD = 7.7). Thrill-seeking males mean age was 29.3 (SD = 8.1) and 26.6 (SD = 5.7) for females. For controls, age for males was 27.9 (SD = 4.2) and 25.6 (SD = 5.17) for females. All Ss were Caucasian. Procedures At the testing time, the S was shown the experimental apparatus and told that their brain waves would be recorded while the S was being shown flashing lights. Ss were previously screened by telephone for type of activity and inclusion criteria. Prior to electrode placement, Ss were given the SSS form IV and a demographic data sheet to complete. VEP procedure The SIM VEP procedure as described by Buchsbaum (1976) was followed. Four light intensities were displayed on a 45 by 33 cm translucent screen located 1 m in front of the Ss: 4, 18, 75, and
JANETL. BLENNER
458
320 footcandles (ft-c). Each light flash had a duration of 500 msec; a total of 256 flashes of white light was presented at 1-set intervals, with 64 trials at each intensity. The order of intensities was randomized with the additional constraint that each intensity be preceded equally often by each of the other three intensities. In addition, eye blinks were monitored and controlled for by digitally subtracting the EOG from the average evoked response. Eye blink parameters were established on each S. Surface gold electrodes were placed on Cz, A2 (right ear), ground and above and below right eye (EOG). Electrode sites were cleaned and abraded to keep resistance under 10,000 R. Ss were tested in a light- and sound-attenuated room. They were instructed to sit quietly, watch the lights and try not to blink. VEP waveforms were smoothed to remove high frequency noise by using the ASYST software package (Adaptable Laboratory Software, Rochester, NY). Three peaks were identified visually by an observer blind to S group or SSS scores. Measurement was at Pl, the most positive peak between 76-l 12 msec; Nl, the most negative between 116156 msec; and P2, the most positive between 1655200 msec; after stimulus onset. Peak to peak amplitudes for PlNl and NlP2 were analyzed separately. In each case, the slope of amplitude as a function of log luminance was evaluated by the method of least squares and served as the evoked potential (EP) measure. Positive slopes over 1.O indicated augmenting and slopes under 1.O indicated reducing. Sensation
seeking
measures
The SSS, form IV (Zuckerman et al., 1980) consists of 72 forced-choice items. It consists of a Gen sensation seeking scale and four subscales derived from factor analysis: TAS is a 1Citem scale indicating a desire to engage in risky sports and activities involving some physical danger, such as mountain climbing or parachuting. ES is an 18-item scale reflecting a taste for sensory experiences in music, art, drug use and travel. Dis is a 1Citem scale reflecting a preference for activities such as partying, drinking, sexual intercourse and gambling. BS is an 18-item scale reflecting an aversion to routine or dull activities. Gen consists of 22 items derived from the four scales. RESULTS EPs
Using a 1.O cutoff for the amplitude intensity slope, the thrill-seeking group had 24 reducers and 35 augmenters. The control group had 32 reducers and 27 augmenters. Differences between the proportion of augmenters and reducers in thrill-seeking versus control groups were not significant on the PlNl lead using Chi-square [x2 (1) = 1.67, NS]. A one-way ANOVA [F(l,l16) = 2.67, NS, MS error = 10.161 of group means was also not significant. Thrill-seeking group mean slope for PlNl was 2.09 (SD = 3.63) and controls was 1.13 (SD = 2.67). Using a 1.O cutoff point for NlP2, the thrill-seeking group had 31 reducers and 28 augmenters. The control group had 15 reducers and 44 augmenters. For the NlP2 lead there was a significant difference between the groups with lower slopes in the thrill seeking group as compared to the control group using chi-square [x2 (1) = 8.02, P < O.OOS] or one-way ANOVA [F(l,l16) = 7.64, P < 0.01, MS error = 7.411. Thrill-seekers’ mean slope was 1.33 (SD = 2.33) and controls was 2.72 (SD = 3.07). It is noteworthy that PlNl and NlP2 slopes were not significantly correlated (r = 0.17, df= 116, NS). Since both PlNl and NlP2 slopes were positively skewed, a non-parametric Mann-Whitney U was performed and confirmed the findings of non-significance for PlNl (U = 1453.5, z = - 1.54, NS) and significance for NlP2 (V = 1244.0, z = -2.67, P < 0.01). Further analyses were done to ascertain any significant differences among the thrill-seeking activity groups. Significant differences between the activity groups were found by using one-way ANOVA’s for PIN1 [F(6,52) = 4.08, P < O.OOS] and NlP2 [F(6,53) = 2.62, P < 0.051. The use of post-hoc Tukey test comparisons of the thrill-seeking groups indicated that on PlNl, rock climbers were significantly lower in their slopes than skydivers and scuba divers (P < 0.05), and hang gliders were significantly lower than scuba divers (P < 0.05). On NlP2, ocean kayakers were significantly lower than skydivers (P < 0.05).
VEP and sensation seeking in thrill-seekers
459
According to Table 1, thrill-seeking activity means on PlNl ranged from the least or most reducing slopes of the motorcycle racer’s and rock climbers to the most augmenting of the scuba divers and ocean kayakers. On NlP2 the scuba and ocean kayakers had the most reducing slopes with the skydivers and ultralight flyers as the most augmenting. However, these results must be viewed with caution as the sample sizes are small. The possibility of additional effects of gender or age category for EP results was examined. A three-way ANOVA was performed. Two-way interactions were found for group (thrill-seeking vs control) with gender for PlNl [F(l,llO) = 4.05, P < 0.051 and age category with gender [F(l,llO) = 4.71, P < 0.051 for PlNl. Age alone was not a factor since there were no significant age category main effects. No significant three-way interaction effects were found. There were significant gender main effects for both PlNl [F(l,llO) = 14.21, P
seeking
On the basis of one-way ANOVA’s between groups, the thrill-seekers were significantly The largest difference was for the Gen greater than controls on all the SSS subscales. scale [F(l,ll3) = 59.02, P c O.OOl] followed by the TAS [F( 1,113) = 56.96, P < O.OOl], ES [F(l,ll3)=49.72, P
n
Mean
NIP2 SD
Mean
SD
Thrill-seekers
Table
I. Mean VEP slopes for thrill-seeking NIP1
(n = 59) Activitv Skydiving Hang-gliding Rock climbing Ultralight flying Scuba diving Ocean kayaking Motorcycle racing
n 20 IO 14 6 4 3 2
Mean 3.76 0.01 -0.06 2.35 5.92 3.91 -0.37
activity
groups
NIP2 SD 3.71 3.23 2.21 2.56 3.26 3.94 1.60
Mean 2.48 0.99 0.72 2.04 0.47 - I .96 0.49
Males Under 30
31
1.15
2.45
1.17
2.16
Over 30
18
1.77
4.08
1.12
1.90
Under 30
6
7.41
3.85
2.52
4.24
Over 30
4
2.79
2.97
1.17
2.01
31 I8
0.90 0.94
2.46 3.02
2.29 2.08
2.29 2.46
6 4
2.65 I .48
2.39 3.25
3.59 7.63
3.60 5.97
F~t?MiC?S
SD 2.53 2.60 1.33 1.89 I .84 I .47 I.58
Controls Males Under 30 Over 30 Females Under 30 Over 30
JANETL. BLENNER
460
Table 3. Mean SSS scores for thrill-seekinn
and control
erouos
Thrill-seekers under 30 SC& Gen Male Female TAS Male Female ES Male Female Dis Male Female BS Male Female
Controls
(’ = 59)
over 30
under 30
Mean
SD
Mean
SD
15.84 18.33
2.90 I.63
16.12 15.50
4.03 5.20
12.65 13.67
I .78 0.52
12.24 12.25
12.00 12.33
3.10 2.25
II.65 II.25
8.06 7.83
3.33 2.86
9.26 10.67
3.04 I .63
-Mean
(’ = 59)
over 30
SD
MeaIl
SD
9.11 10.25
4.61 6.34
10.50 12.00
4.85 6.78
2.33 I.50
8.55 8.75
3.89 4.92
8.50 8.25
2.94 4.99
4.12 5.12
6.65 7.50
3.39 3.70
1.78 10.25
2.61 6.65
6.71 5.50
2.52 2.38
4.74 2.00
2.31 1.83
5.78 6.25
I .90 4.72
10.12 10.25
3.69 3.50
6.03 6.15
2.92 3.59
6.17 1.25
2.31 3.59
while BS (0.18) and GSS ( - 0.02) did not contribute much. Classification analysis indicated that 83.5% of the Ss could be correctly grouped on the basis of the SSS scores. Further analysis was performed by one-way ANOVA’s on the 7 thrill-seeking group activities for SSS scores but no significant differences were found. Since these results may be attributed to the cells being too small, the tests were repeated with only the four largest subgroups (skydiving, hang-gliding, rock climbing, and ultralight). However, there were still no significant differences on any of the SSS scales. The relevant means for each of the thrill-seeking activity groups and controls are reported in Table 4. Three way ANOVA’s were performed for group (thrill-seeking and control), age category, and gender for all the SSS subscales. No age category or gender main effects were significant. The ANOVA’s yielded only one significant interaction effect, group by age for Dis [F(1,107) = 8.50, P < O.OOS]. Table 3 reports means of SSS subscales by age category and gender for thrill-seekers and controls. On Dis the under 30 thrill-seekers had comparable means although not high, males were 3 points greater than control males and thrill-seeker females were 5.85 mean points greater than control females. Over 30 groups were comparable on Dis. DISCUSSION Thrill seekers had lower NlP2 but not PlNl slopes than controls. Although both groups showed a predominance of augmenters, thrill-seekers showed significantly less augmentation than non-thrill-seekers on NlP2. Both PlNl and NlP2 components did not significantly correlate with each other. This lack of significance between components and an opposite trend on each component warrants the need for additional studies utilizing both components with a wider range of intensities, including higher intensities than were used in this study. However, this study’s use of the customary Buchsbaum VEP paradigm of moderate intensities, vertex lead, and PIN1 component showed a predominance of VEP augmenters rather than reducers among the thrill-seekers. This finding provides evidence for augmentation in a behaviorally high sensation seeking group. Table 4. Mean SSS scale for thrill-seeking
activity
wows
ES
TAS
Gen Activity
Mean
SD
Mcao
SD
Mean
SD
Skydiving Hang-gliding Rock climbers Ultralight Scuba Ocean kayaking Motorcycle racing Thrill-seeking overall Control
15.37 16.10 17.00 17.50 14.25 16.67 17.00 16.15 IO.19
3.90 3.70 2.88 2.88 3.30 2.08 1.41 3.35 4.85
12.16 13.00 12.64 12.33 12.50 14.00 13.50 12.60 8.53
2.19 I .25 2.41 I .03 I .29 0.00 0.71 I .87 3.66
Il.26 II.50 13.50 12.67 10.75 9.00 12.50 II.88 7.32
3.75 4.03 2.35 3.56 2.21 3.61 3.54 3.42 3.52
7.84 6.50 7.85 6.61 6.75 9.00 7.50 7.41 4.98
group
BS
Dis MeaIl
SD
Mean
SD
2.67 3.10 3.01 2.73 I.71 4.36 9.19 3.04 2.54
9.05 10.40 10.64 IO.16 9.25 8.67 7.50 9.72 6.21
2.81 3.5 3.05 3.05 2.75 4.04 0.7 I 3.14 2.77
VEP and sensation seeking in thrill-seekers Table 5. Correlations Scale Gen Thrill-seekers Gen TAS ES Dis BS Control Gen TAS ES Dis BS
(n = 59) 0.78***
Two-tailed
statistical
between SSS scales and VEP
ES
Dis
BS
NIPI
0.69*‘* 0.19 NS
0.19NS 0.15NS 0.27’
0.65”’ 0.21 NS 0.70”’ 0.301
0.06 NS 0.08 NS 0.04 NS 0.26’ 0.06 NS
0.76”’ 0.47***
0.26. 0.26’ 0.35”
0.66.” 0.45*** 0.73*** 0.24 NS
0.07 NS -0.02 NS 0.001 NS 0.06 NS 0.06 NS
TAS fn = 59) ’ 0.57*;*
461
significance:
*P < 0.05; **P
< 0.01;
l**P
NIP2 0.03 NS -0.15NS 0.13NS 0.06 NS 0.07 NS -0.002 NS -0.007 NS 0.05 NS 0.08 NS -0.04 NS
< 0.001.
Interestingly, significant differences were found among the thrill-seeking activity groups for both VEP components; no significant differences were found for any of the SSS scales. Although all of these sports are high-risk, they vary widely in required motor and perceptual skills. The VEP differences among the groups may reflect individual differences in perceptual organization not tapped by written attitudinal scales. A gender effect was present in both VEP components: females showed more of an augmenting response in both thrill-seeking and control groups than the males. However, even when gender was included in the model, no significant differences were found on PlNl between thrill-seeking and control groups. The only significant relationship between VEP and SSS was augmentation with the Dis scale, but this occurred only in the thrill-seeker group for PlNl. This modest correlation (0.29) is consistent with the results of other studies (Zuckerman et al., 1974; Von Knorring, 1981) which also found this relationship with the Dis scale on PlNl but used different VEP procedures. However, Zuckerman’s claim (1984a, p. 417) that a low score on the Dis scale as being associated with a protective cortical mechanism congruent with stimulus avoidance behavior is questionable. The mean Dis scores of the thrill-seekers in this study were relatively low compared to other SSS scores, while by definition, they were not stimulus avoiders. In addition, the results of this study provide no support of an association between VEP and other dimensions of SSS (including Gen), as most of the correlations were near zero. Yet, the only scale to demonstrate reasonable internal consistency reliability was Dis, which may contribute to its being the only significant correlate of VEP. Thrill seekers scored significantly higher than controls on all the SSS scales. These findings are in agreement with other studies of high-risk participants (e.g. Hymbaugh & Garrett, 1974; Bacon, 1974; Kusysyzn et al., 1973; Connolly, 1981; Straub, 1982). It is noteworthy that TAS was the most important scale in differentiating thrill-seekers from controls. This finding provides behavioral evidence in favor of the construct validity of the TAS scale. The robust thrill-seeker scores and discriminating capacity of TAS may indicate that although thrill-seekers usually participate in one specific sport, they have an overall preference for all types of high-risk sports. This can be interpreted as providing support for TAS as an overall personality trait that is manifested in a general desire to engage in many types of high-risk sports. Although thrill-seekers scored significantly higher on all the SSS scales, the lack of significant relationships between TAS and any of the other SSS scales (except Gen) in the thrill-seeking group, and TAS as the primary discriminator between the groups provides evidence for a more specific thrill-seeking trait rather than a broader trait of sensation seeking in thrill-seekers. This is especially true since all SSS subscales are reported to be intercorrelated (Zuckerman, 1979). One can speculate that thrill-seekers as sensation seekers may be attracted to, and specifically channel their need for sensation into, one dimension of sensation seeking: thrill-seeking. The nature of these thrill-seeking activities may provide the high sensations needed for optimal stimulation. Scores on the Gen scale were highly correlated with those on the TAS, ES and BS scales, in both groups, which is consistent with Zuckerman’s et al. (1974, p. 95) findings. The lack of a significant relationship between Dis and Gen scores in the thrill-seeking group may be attributed to the Gen overlapping with only these three scales and not Dis. This lends further support to Zuckerman’s
462
JANET L. BLENNER
(1979) criticism of Gen in SSS form IV as not being a satisfactory measure of overall sensation seeking. The dimensions of the SSS reflect some atypical characteristics of thrill-seekers. The lack of age effects on Gen and TAS scores is different from the effects seen in most SSS studies of the general population (Zuckerman, Eysenck & Eysenck, 1978; Zuckerman, 1979) which report higher thrill-seeking preference in younger males, with a steady decline through adulthood into old age. In this study, interest in TAS was evident even in the older age group. Zuckerman (1984, p. 433) speculated that accessibility for sensation seeking outlets may determine the nature of sensation seeking. His focus was the social class of individuals, and he proposed that the middle class may have more accessibility to sport activities, enabling the members of this class to meet their needs for sensation. All the thrill-seekers in this study were middle class, which supports this contention. In addition, the climate, terrain, and the availability of these types of high-risk activities must be considered. Southern California provides a climate and many different terrains which are supportive of a wide array of thrill-seeking activities all year round. Environmental accessibility coupled with socio-economic class may play significant roles in the channeling of sensation seeking. In conclusion, it is suggested that further research be conducted on the relationship of VEP and SSS using consistent VEP procedures ensuring adequate comparisons of findings. Future thrillseeking studies need to include females and explore the uniqueness of this particular population as related to the sensation seeking construct. Acknowledgemenfs~I would like to acknowledge Drs Monte Buchsbaum and Richard Haier for their editorial suggestions. I would also like to acknowledge Tony Paquin and Judith Rivera for their assistance with data collection and Paul Clopton for his statistical assistance.
REFERENCES Bacon, J. (1974). Sensation seeking levels for members of high-risk organizations. Unpublished manuscript (Described in Zuckerman, 1979, 207-208). Bouter, L. M., Knipschild, P. G., Feij, J. A. & Volovics, A. (1988). Sensation seeking and injury risk in downhill skiing. Personality and Individual Differences, 3, 667-673. Buchsbaum, M. (1976). Self-regulation of stimulus intensity: Augmenting/reducing and the average evoked response. In Schwartz, G. & Shapiro, D. (Eds), Consciousness and self-regulation. New York: Plenum Press. Buchsbaum, M. & Pfefferbaum, A. (1971). Individual differences in stimulus intensity response. Psychophysiology, 8, 600-611. Buchsbaum, M. S. & Silverman, J. (1968). Stimulus intensity control and cortical evoked potentials. Psychosomatic Medicine, 30, 12-22. Connolly, P. M. (1981). An exploratory study of adults engaging in the high-risk sport of skiing. Master’s Thesis, Rutgers University. Coursey, R. D., Buchsbaum, N. S. & Frankel, B. L. (1975). Personality measures and evoked responses in chronic insomniacs. Journal of Abnormal Psychology, 84, 239-249. Cronin, C. (1991). Sensation seeking among mountain climbers. Personality and Individual Differences, 12, 653454. Davis, C., Cowles, M. & Kohn, P. (1983). Strength of the nervous system and augmenting-reducing: Paradox lost. Personality and Individual Differences, 4, 491498. Eysenck, H. J. (1955). Cortical inhibition, figural aftereffect and theory of personality. Journal of Abnormal Social Psychology, 51, 94-106. Haier, R. J. (1984). Sensation seeking and augmenting-reducing: Does a nerve have nerve? Behavioral and Brain Sciences, 7,441*2. Haier, R. J., Robinson, D. L., Braden, W. & Williams, D. (1984). Evoked potential augmenting-reducing and personality differences. Personality and Individual Differences, 5, 293-301. Hall, R. A., Rappaport, M., Hopkins, H. K., Griffin, R. B. & Silverman, J. (1970). Evoked response and behaviour in cats. Science, 170, 998-1000. Hymbaugh, K. & Garrett J. (1974). Sensation seeking among skydivers. Perceptual Motor Skills, 38, 118. Knorring, L. von (1981). Visual average evoked response and platelet monamine oxidase in patients suffering from alcoholism. In Beglenter, H. (Ed.), Biological effects of alcohol (pp. 649460). New York: Plenum Press. Kusysyzn, I., Steinberg, P. & Elliott, B. (1973). Arousal seeking, physical risk taking and personality. Unpublished manuscript (Described in Zuckerman, 1979, 206). Lukas, J. H. (1987). Visual evoked potential augmenting-reducing and personality: The vertex augmenter is a sensation seeker. Personality and Individual Differences, 8, 385-395. Lukas, J. H. & Mullins, L. F. (1983). Auditory augmenting-reducing and sensation seeking. Pyschophysiology, 20, 457. Lukas, J. H. & Mullins, L. F. (1985). Auditory augments are sensation seekers and perform better under high work loads. Psychophysiology, 22, 58(t58 1. Lukas, J. & Siegel, J. (1977). Cortical mechanisms that augment or reduce evoked potentials in cats. Science, 198, 73-75. Mullins, L. F. & Lukas, J. H. (1984). Auditory augmenters are sensation seekers if they attend the stimuli. Psychophysiology, 21, 589.
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seeking
in thrill-seekers
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Orlebeke, J. F., Kok, A. & Zeillemaker, C. W. (1989). Disinhibition and the processing of auditory stimulus intensity: An erp study. Personality and Individual Differences, IO, 445-451. Petrie, A. (1960).Some psychological aspects of pain and relief of suffering. Annuals of the New York Academy of Science, 86, 13-27. Petrie, A. (1967). Individuality in pain and suffering. Chicago: University of Chicago Press. Petrie, A., Collins, W. & Solomon, P. (1958). Pain sensitivity, sensory deprivation and susceptibility to satiation. Science, 128, 1431-1433. Sales, S. (1971). Need for stimulation as a factor in social behavior. Journal of Personality and Social Psychology, 19, 124134. Sales, S. (1972). Need for stimulation as a factor in preference for different stimuli. Journal of Personalify Assessment, 36, 5661. Silverman, J., Buchsbaum, M. & Henkin, R. (1969). Stimulus sensitivity and stimulus intensity control. Perceptual Motor Skills, 28, 71-78. Sternberg, G., Rosen, I. & Risberg, J. (1988). Personality and augmenting/reducing in visual and auditory evoked potentials. Personality and Individual Differences, 9, 571-579. Straub, W. F. (1982). Sensation seeking among high and low-risk female athletes. Journal of Sport Psychology, 4, 246253. Zuckerman, M. (1979). Sensation seeking: Beyond the optimal level of arousal. New York: Erlbaum. Zuckerman, M. (1983). Sensation seeking and sports. Personality and Individual Differences, 4, 2855293. Zuckerman, M. (1984a). Sensation seeking: A comparative approach to a human trait. Behavioral and Brain Sciences, 7, 413471. Zuckerman, M. (1984b). The findings and sensation seeking: EP augmenting and sensation seeking. Behavioral and Brain Science, 7, 459461. Zuckerman, M. (1990). The psychophysiology of sensation seeking. Journal of Personality, 58, 313-345. Zuckerman, M., Buchsbaum, M. S. & Murphy, D. L. (1980). Sensation seeking and its biological correlates. Psychological Bulletin, 88, 1877214. Zuckerman, M., Eysenck, S. B. G. KL Eysenck, H. J. (1978). Sensation seeking in England and America: Cross-cultural, age and sex comparisons. Journal of Consulting and Clinical Psychology, 39, 308-321. Zuckerman, M., Murtaugh, T. M. SC Siegel, J. (1974). Sensation seeking and cortical augmenting-reducing. Psychophysiology, II, 535-542. Zuckerman, M., Simons, R. F. & Como, P. G. (1988). Sensation seeking and stimulus intensity as modulators of cortical, cardiovascular, and electrodermal response: A cross-modality study. Personality and Individual Differences, 9, 361-372. Zuckerman, M., Kolin, E. A., Price, L. & Zoob, I. (1964). Development of a sensation seeking scale. Journal of Consulting and Clinical Psychology, 28, 477482.
0191-8869/93 $6.00+ 0.00 Copyright 0 1993Pergamon Press Ltd
1993
VISUAL EVOKED POTENTIAL STIMULUS INTENSITY MODULATION AND SENSATION SEEKING IN THRILL-SEEKERS JANET L. BLENNER College of Health and Human Services, San Diego State University, (Received
IO November
San Diego, CA 92182-0254,
1991; received for publication
U.S.A
30 June 1993)
Summary-Visual
evoked potentials (VEPs) to stimuli of four intensities of 4, 18, 75, and 320 footcandles (ft-c) were recorded and Zuckerman’s sensation seeking scale (SSS) was administered to 59 thrill-seekers and 59 non-thrill-seeker control subjects. The thrill-seekers were a heterogeneous group composed of skydivers, hang-gliders, rock climbers, ultralight flyers, scuba divers, motorcycle racers, and ocean kayakers. Amplitude/intensity function slopes were computed PIN1 and NIP2 components on lead Cz. Thrill-seekers had significantly lower slope on NIP2 but were not significantly different from controls on PIN 1.The only significant correlation between VEP and SSS was for the disinhibition scale (Dis) on PIN 1 (0.29). Thrill-seekers were significantly higher than controls on all of the SSS subscales. Thrill-seekers’ highest mean score was reported on the thrill and adventure seeking scale (TAS). TAS also discriminated the best between the groups. Female thrill-seekers less than 30 years old had mean scores higher than their male counterparts on all SSS scales except Dis.
INTRODUCTION
Origins of stimulus intensity modulation can be found in the work of Eysenck (1953, who developed the notion that extraverts show more satiation effects than introverts. Petrie (1960) extended this notion into a theory of perceptual reactance. Petrie (1967) devised the Kinesthetic Figural Aftereffect (KFA), a psychophysical measure of the construct, where Ss judge the size of a stimulation block. Central nervous system (CNS) augmenters tend to subjectively increase in poststimulation block-size judgment while CNS reducers subjectively decrease in their judgment size. Buchsbaum and Silverman (1968) developed a visual evoked potential (VEP) procedure as a measure of the construct and coined the term stimulus intensity modulation. They demonstrated correlations between KFA and VEP measures. The theory of stimulus intensity modulation presupposes that each person has a subjective tendency to react to various intensities of stimuli that is directly related to the ability of the person’s nervous system to modulate responses. Essentially, individuals differ in the way they react to various intensities of environmental stimuli. When light intensity is viewed from dim to bright, the VEP amplitude response may increase or decrease at different rates. Persons are classified as either cortical augmenters, those in whom the VEP amplitude response increases, or cortical reducers, those in whom the response to the same series of increasing stimulus intensities decreases (Silverman, Buchsbaum & Henkin, 1969; Buchsbaum & Pfefferbaum, 1971). The traditional Buchsbaum (1976) procedure for measuring stimulus intensity modulation commonly uses visual stimuli and measures at the slope of the vertex PlO(rN120 amplitude. Positive slopes define the augmenting end of the continuum, and less positive and even negative slopes define the reducing end. Zuckerman’s sensation seeking is based on constructs of optimal levels of stimulation devoted to maintaining optimal levels of arousal. Sensation seeking is described by Zuckerman (1979) as a trait reflected in the “need for varied, novel, and complex sensations and experiences and the willingness to undertake physical and social risks for the sake of such experiences” (p. 10). Zuckerman, Kolin, Price and Zoob (1964) devised the original sensation seeking scale (SSS). According to the measure, individuals high in sensation seeking are thought to respond as though stimuli are less intense and tend to prefer experiences that are intense, unusual or unpredictable or that have an edge of danger (Zuckerman, 1984a). They have an aversion to routine and are open to changes from their usual environment if the changes facilitate new experiences (Zuckerman, 455
456
JANETL. BLENNER
Murtaugh & Siegel, 1974). Zuckerman (1983) contends that sensation seeking is relevant to sports involving high levels of personal risk and novel sensations. He suggests that skydiving and scuba diving would be some of the sports tailored to people with a high sensation seeking trait. Zuckerman (1979) states, “It would not be surprising to find that persons who actually engage in these (high-risk sport) activities . . . score high on SSS” (p. 206). Thrill-seekers engage in sports in which the risk of physical injury and even death to participants is high. Most studies of thrill-seekers have focused on the S’s personality and motivation to participate in these sports. Some researchers have administered the SSS to thrill-seekers and to persons in high-risk occupations. Hymbaugh and Garrett (1974) gave the original SSS to skydivers and matched controls and found that the skydivers scored higher than the controls on the total (Tot) score. In a study by Straub (1982), auto racers had the highest scores on the SSS form V, followed by hang gliders, and last were bowlers. The experience seeking (ES) scale followed by boredom susceptibility (BS) and thrill and adventure seeking (TAS) differentiated the groups the most. Kusysyzn, Steinberg and Elliot (1973) compared a mixed group of men involved in risk-taking occupations and sports, including firemen, riot squad policemen, race car drivers, skydivers and snowmobilers, with a control group and found those involved in risk taking scored higher on the General (Gen) and TAS scales of the SSS form IV. Bacon (1974) administered the SSS form IV to divers and firemen who are often engaged in high-risk activity and to control Ss. Both high-risk groups were significantly higher than the control group on the Gen, disinhibition (Dis) and BS scales. However, only the divers were higher on the TAS scale. Neither high-risk group was significantly higher than the control group on the ES scale. Connolly (1981) studied recreational skiers, ski instructors and non-skiers and found that of the three groups, ski instructors had the highest scores on the total SSS, ES and TAS scales of the SSS form V. Bouter, Knipschild, Feij and Volovics (1988) administered a Dutch version of the SSS to skiers and found them to have higher TAS scores than non-skiers. Cronin (1991) found that mountain climbers scored higher on the Tot, ES and TAS scales of the SSS form V than control Ss. The relationship of stimulus intensity modulation and sensation seeking has been viewed from two theoretical perspectives. From Petrie’s (1960) perspective, reducers are stimulus deprived and should seek out complex and intense stimulus situations. Augmenters amplify sensory experience and should prefer low stimuli and are likely to seek out and respond favorably to quiet and dull stimulus situations. This perspective has been upheld by KFA studies (e.g. Petrie, Collins & Solomon, 1958; Sales, 1971, 1972). Zuckerman (e.g. Zuckerman, 1979; Zuckerman, Buchsbaum & Murphy, 1980) take the opposite position: that evoked potential augmenters increase afferent stimuli and seek sensations to satisfy a high optimal arousal level and reducers decrease stimulation and avoid sensations to satisfy a low optimal arousal level. The differences between the two positions have been attributed to semantics with Petrie defining augmenting-reducing as a subjective experience, and Buchsbaum and Zuckerman defining it as a physiological response (Davis, Cowles & Kohn, 1983). Essentially, KFA augmenters are evoked potential reducers. In spite of this explanation, evoked potential studies alone have had conflicting findings. (For a review and in depth discussion of all the evoked potential studies with SSS, see Zuckerman, 1990.) Using VEP procedures, Haier, Robinson, Braden and Williams (1984) found reducing related to high scores on all the SSS scales except Dis which did not differentiate augmenters from reducers. Four studies (Sternberg, Rosen & Risberg, 1988; von Knorring, 1981; Zuckerman, Murtaugh & Siegel, 1974; Zuckerman, Simons & Como, 1988) found VEP augmenting related to the Dis scale. Lukas (1987) found VEP augmentation related to the Tot scale while Coursey, Buchsbaum and Frankel (1975) found this relationship with the Gen scale. In addition, two studies (Hall, 1970; Lukas & Siegel, 1977) found a relationship Rappaport, Hopkins, Griffin & Silverman, between VEP augmenting and behavioral ratings of sensation seeking in cats. Significant findings were also found for some auditory evoked potential (AEP) studies with SSS. Zuckerman et al. (1988) found a relationship between AEP augmenting with Dis while von Knorring (1981) found this relationship with both Dis and Gen scales. Coursey et al. (1975) found a significant relationship between Gen and AEP augmenting in a study of insomnia. In attention conditions, Lukas and Mullins (1983) did not find a relationship between any of the SSS scales
VEP and sensation
seeking
in thrill-seekers
457
in their initial study, however subsequent studies found an augmenting relationship with Dis and Tot (Mullins & Lukas, 1984) and ES, BS and Tot (Lukas & Mullins, 1985). Orlebeke, Kok and Zeillemaker (1989) found a relationship between low augmenting and high Dis in both passive and active conditions. It must be noted that variance existed between the aforementioned studies as to their procedures, conditions, and components used in the analysis. Haier et al. (1984) have criticized these findings as to their deviation from the customary Buchsbaum (1976) VEP procedure which they claim contribute to problems in defining augmenting and reducing. The problem is perceived as being the variance among laboratories as to their use of different intensities, durations, and stimulation procedures while claiming to measure the same phenomenon. Discussion of these paradigm differences can be found in Haier (1984) and Zuckerman (1984b). Only Haier et al. (1984) used the customary Buchsbaum (1976) VEP apparatus and procedure. The aim of this present study is to relate VEP (using the customary Buchsbaum apparatus and procedure) and SSS to individual differences in sensation seeking behavior rather than only personality SSS scale scores and answer the following questions: (1) Do behaviorally high sensation seekers (thrill-seekers) have significantly greater VEP augmentation or reduction than non-thrillseeking control Ss? (2) Is sensation seeking as measured by the SSS related to VEP augmentation or reduction? (3) Do behaviorally high sensation seekers (thrill-seekers) score significantly higher than non-thrill-seeking control Ss on the SSS dimensions. 7 This study will also contribute information to the construct validity of the SSS and meet Zuckerman’s (1983) call for studies relating sensation seeking to risk-taking sports.
METHOD Subjects One hundred and eighteen volunteer Ss from Southern California completed the testing as described below. Of that sample, 59 were thrill-seekers (male = 49; female = 10). The remaining 59 were non-thrill-seeker control Ss who were selected to balance with the thrill-seeking group with respect to age (under and over 30 years) and gender. Thrill-seekers were recruited by addressing thrill-seeking clubs and organizations and placing local newspaper ads and flyers in adventure equipment and travel stores in San Diego, California. Thrill-seeker Ss needed to meet the following criteria to be included in the study: participation in a high-risk sport on a regular, ongoing basis for a minimum of 1 year and no previous history of major visual or neurological problems. Non-thrill-seeker control Ss were recruited from both undergraduate and graduate students and staff from local universities. They were not currently or previously engaged in high-risk sports. They were also screened by medical history for any neurological or visual problems. Thrill-seeking Ss represented the following groups: skydivers (n = 20) hang-gliders (n = lo), rock climbers (n = 14); ultralight flyers (n = 6); high-risk scuba divers (n = 4); motorcycle racers (n = 2); and ocean kayakers (n = 3). Of the female thrill-seekers (n = 10) there were 5 skydivers, 1 hang glider, 1 rock climber, 2 scuba divers and 1 ocean kayaker. Thrill-seekers’ age range was 19-59 years (mean = 28.9; SD = 7.7). Thrill-seeking males mean age was 29.3 (SD = 8.1) and 26.6 (SD = 5.7) for females. For controls, age for males was 27.9 (SD = 4.2) and 25.6 (SD = 5.17) for females. All Ss were Caucasian. Procedures At the testing time, the S was shown the experimental apparatus and told that their brain waves would be recorded while the S was being shown flashing lights. Ss were previously screened by telephone for type of activity and inclusion criteria. Prior to electrode placement, Ss were given the SSS form IV and a demographic data sheet to complete. VEP procedure The SIM VEP procedure as described by Buchsbaum (1976) was followed. Four light intensities were displayed on a 45 by 33 cm translucent screen located 1 m in front of the Ss: 4, 18, 75, and
JANETL. BLENNER
458
320 footcandles (ft-c). Each light flash had a duration of 500 msec; a total of 256 flashes of white light was presented at 1-set intervals, with 64 trials at each intensity. The order of intensities was randomized with the additional constraint that each intensity be preceded equally often by each of the other three intensities. In addition, eye blinks were monitored and controlled for by digitally subtracting the EOG from the average evoked response. Eye blink parameters were established on each S. Surface gold electrodes were placed on Cz, A2 (right ear), ground and above and below right eye (EOG). Electrode sites were cleaned and abraded to keep resistance under 10,000 R. Ss were tested in a light- and sound-attenuated room. They were instructed to sit quietly, watch the lights and try not to blink. VEP waveforms were smoothed to remove high frequency noise by using the ASYST software package (Adaptable Laboratory Software, Rochester, NY). Three peaks were identified visually by an observer blind to S group or SSS scores. Measurement was at Pl, the most positive peak between 76-l 12 msec; Nl, the most negative between 116156 msec; and P2, the most positive between 1655200 msec; after stimulus onset. Peak to peak amplitudes for PlNl and NlP2 were analyzed separately. In each case, the slope of amplitude as a function of log luminance was evaluated by the method of least squares and served as the evoked potential (EP) measure. Positive slopes over 1.O indicated augmenting and slopes under 1.O indicated reducing. Sensation
seeking
measures
The SSS, form IV (Zuckerman et al., 1980) consists of 72 forced-choice items. It consists of a Gen sensation seeking scale and four subscales derived from factor analysis: TAS is a 1Citem scale indicating a desire to engage in risky sports and activities involving some physical danger, such as mountain climbing or parachuting. ES is an 18-item scale reflecting a taste for sensory experiences in music, art, drug use and travel. Dis is a 1Citem scale reflecting a preference for activities such as partying, drinking, sexual intercourse and gambling. BS is an 18-item scale reflecting an aversion to routine or dull activities. Gen consists of 22 items derived from the four scales. RESULTS EPs
Using a 1.O cutoff for the amplitude intensity slope, the thrill-seeking group had 24 reducers and 35 augmenters. The control group had 32 reducers and 27 augmenters. Differences between the proportion of augmenters and reducers in thrill-seeking versus control groups were not significant on the PlNl lead using Chi-square [x2 (1) = 1.67, NS]. A one-way ANOVA [F(l,l16) = 2.67, NS, MS error = 10.161 of group means was also not significant. Thrill-seeking group mean slope for PlNl was 2.09 (SD = 3.63) and controls was 1.13 (SD = 2.67). Using a 1.O cutoff point for NlP2, the thrill-seeking group had 31 reducers and 28 augmenters. The control group had 15 reducers and 44 augmenters. For the NlP2 lead there was a significant difference between the groups with lower slopes in the thrill seeking group as compared to the control group using chi-square [x2 (1) = 8.02, P < O.OOS] or one-way ANOVA [F(l,l16) = 7.64, P < 0.01, MS error = 7.411. Thrill-seekers’ mean slope was 1.33 (SD = 2.33) and controls was 2.72 (SD = 3.07). It is noteworthy that PlNl and NlP2 slopes were not significantly correlated (r = 0.17, df= 116, NS). Since both PlNl and NlP2 slopes were positively skewed, a non-parametric Mann-Whitney U was performed and confirmed the findings of non-significance for PlNl (U = 1453.5, z = - 1.54, NS) and significance for NlP2 (V = 1244.0, z = -2.67, P < 0.01). Further analyses were done to ascertain any significant differences among the thrill-seeking activity groups. Significant differences between the activity groups were found by using one-way ANOVA’s for PIN1 [F(6,52) = 4.08, P < O.OOS] and NlP2 [F(6,53) = 2.62, P < 0.051. The use of post-hoc Tukey test comparisons of the thrill-seeking groups indicated that on PlNl, rock climbers were significantly lower in their slopes than skydivers and scuba divers (P < 0.05), and hang gliders were significantly lower than scuba divers (P < 0.05). On NlP2, ocean kayakers were significantly lower than skydivers (P < 0.05).
VEP and sensation seeking in thrill-seekers
459
According to Table 1, thrill-seeking activity means on PlNl ranged from the least or most reducing slopes of the motorcycle racer’s and rock climbers to the most augmenting of the scuba divers and ocean kayakers. On NlP2 the scuba and ocean kayakers had the most reducing slopes with the skydivers and ultralight flyers as the most augmenting. However, these results must be viewed with caution as the sample sizes are small. The possibility of additional effects of gender or age category for EP results was examined. A three-way ANOVA was performed. Two-way interactions were found for group (thrill-seeking vs control) with gender for PlNl [F(l,llO) = 4.05, P < 0.051 and age category with gender [F(l,llO) = 4.71, P < 0.051 for PlNl. Age alone was not a factor since there were no significant age category main effects. No significant three-way interaction effects were found. There were significant gender main effects for both PlNl [F(l,llO) = 14.21, P
seeking
On the basis of one-way ANOVA’s between groups, the thrill-seekers were significantly The largest difference was for the Gen greater than controls on all the SSS subscales. scale [F(l,ll3) = 59.02, P c O.OOl] followed by the TAS [F( 1,113) = 56.96, P < O.OOl], ES [F(l,ll3)=49.72, P
n
Mean
NIP2 SD
Mean
SD
Thrill-seekers
Table
I. Mean VEP slopes for thrill-seeking NIP1
(n = 59) Activitv Skydiving Hang-gliding Rock climbing Ultralight flying Scuba diving Ocean kayaking Motorcycle racing
n 20 IO 14 6 4 3 2
Mean 3.76 0.01 -0.06 2.35 5.92 3.91 -0.37
activity
groups
NIP2 SD 3.71 3.23 2.21 2.56 3.26 3.94 1.60
Mean 2.48 0.99 0.72 2.04 0.47 - I .96 0.49
Males Under 30
31
1.15
2.45
1.17
2.16
Over 30
18
1.77
4.08
1.12
1.90
Under 30
6
7.41
3.85
2.52
4.24
Over 30
4
2.79
2.97
1.17
2.01
31 I8
0.90 0.94
2.46 3.02
2.29 2.08
2.29 2.46
6 4
2.65 I .48
2.39 3.25
3.59 7.63
3.60 5.97
F~t?MiC?S
SD 2.53 2.60 1.33 1.89 I .84 I .47 I.58
Controls Males Under 30 Over 30 Females Under 30 Over 30
JANETL. BLENNER
460
Table 3. Mean SSS scores for thrill-seekinn
and control
erouos
Thrill-seekers under 30 SC& Gen Male Female TAS Male Female ES Male Female Dis Male Female BS Male Female
Controls
(’ = 59)
over 30
under 30
Mean
SD
Mean
SD
15.84 18.33
2.90 I.63
16.12 15.50
4.03 5.20
12.65 13.67
I .78 0.52
12.24 12.25
12.00 12.33
3.10 2.25
II.65 II.25
8.06 7.83
3.33 2.86
9.26 10.67
3.04 I .63
-Mean
(’ = 59)
over 30
SD
MeaIl
SD
9.11 10.25
4.61 6.34
10.50 12.00
4.85 6.78
2.33 I.50
8.55 8.75
3.89 4.92
8.50 8.25
2.94 4.99
4.12 5.12
6.65 7.50
3.39 3.70
1.78 10.25
2.61 6.65
6.71 5.50
2.52 2.38
4.74 2.00
2.31 1.83
5.78 6.25
I .90 4.72
10.12 10.25
3.69 3.50
6.03 6.15
2.92 3.59
6.17 1.25
2.31 3.59
while BS (0.18) and GSS ( - 0.02) did not contribute much. Classification analysis indicated that 83.5% of the Ss could be correctly grouped on the basis of the SSS scores. Further analysis was performed by one-way ANOVA’s on the 7 thrill-seeking group activities for SSS scores but no significant differences were found. Since these results may be attributed to the cells being too small, the tests were repeated with only the four largest subgroups (skydiving, hang-gliding, rock climbing, and ultralight). However, there were still no significant differences on any of the SSS scales. The relevant means for each of the thrill-seeking activity groups and controls are reported in Table 4. Three way ANOVA’s were performed for group (thrill-seeking and control), age category, and gender for all the SSS subscales. No age category or gender main effects were significant. The ANOVA’s yielded only one significant interaction effect, group by age for Dis [F(1,107) = 8.50, P < O.OOS]. Table 3 reports means of SSS subscales by age category and gender for thrill-seekers and controls. On Dis the under 30 thrill-seekers had comparable means although not high, males were 3 points greater than control males and thrill-seeker females were 5.85 mean points greater than control females. Over 30 groups were comparable on Dis. DISCUSSION Thrill seekers had lower NlP2 but not PlNl slopes than controls. Although both groups showed a predominance of augmenters, thrill-seekers showed significantly less augmentation than non-thrill-seekers on NlP2. Both PlNl and NlP2 components did not significantly correlate with each other. This lack of significance between components and an opposite trend on each component warrants the need for additional studies utilizing both components with a wider range of intensities, including higher intensities than were used in this study. However, this study’s use of the customary Buchsbaum VEP paradigm of moderate intensities, vertex lead, and PIN1 component showed a predominance of VEP augmenters rather than reducers among the thrill-seekers. This finding provides evidence for augmentation in a behaviorally high sensation seeking group. Table 4. Mean SSS scale for thrill-seeking
activity
wows
ES
TAS
Gen Activity
Mean
SD
Mcao
SD
Mean
SD
Skydiving Hang-gliding Rock climbers Ultralight Scuba Ocean kayaking Motorcycle racing Thrill-seeking overall Control
15.37 16.10 17.00 17.50 14.25 16.67 17.00 16.15 IO.19
3.90 3.70 2.88 2.88 3.30 2.08 1.41 3.35 4.85
12.16 13.00 12.64 12.33 12.50 14.00 13.50 12.60 8.53
2.19 I .25 2.41 I .03 I .29 0.00 0.71 I .87 3.66
Il.26 II.50 13.50 12.67 10.75 9.00 12.50 II.88 7.32
3.75 4.03 2.35 3.56 2.21 3.61 3.54 3.42 3.52
7.84 6.50 7.85 6.61 6.75 9.00 7.50 7.41 4.98
group
BS
Dis MeaIl
SD
Mean
SD
2.67 3.10 3.01 2.73 I.71 4.36 9.19 3.04 2.54
9.05 10.40 10.64 IO.16 9.25 8.67 7.50 9.72 6.21
2.81 3.5 3.05 3.05 2.75 4.04 0.7 I 3.14 2.77
VEP and sensation seeking in thrill-seekers Table 5. Correlations Scale Gen Thrill-seekers Gen TAS ES Dis BS Control Gen TAS ES Dis BS
(n = 59) 0.78***
Two-tailed
statistical
between SSS scales and VEP
ES
Dis
BS
NIPI
0.69*‘* 0.19 NS
0.19NS 0.15NS 0.27’
0.65”’ 0.21 NS 0.70”’ 0.301
0.06 NS 0.08 NS 0.04 NS 0.26’ 0.06 NS
0.76”’ 0.47***
0.26. 0.26’ 0.35”
0.66.” 0.45*** 0.73*** 0.24 NS
0.07 NS -0.02 NS 0.001 NS 0.06 NS 0.06 NS
TAS fn = 59) ’ 0.57*;*
461
significance:
*P < 0.05; **P
< 0.01;
l**P
NIP2 0.03 NS -0.15NS 0.13NS 0.06 NS 0.07 NS -0.002 NS -0.007 NS 0.05 NS 0.08 NS -0.04 NS
< 0.001.
Interestingly, significant differences were found among the thrill-seeking activity groups for both VEP components; no significant differences were found for any of the SSS scales. Although all of these sports are high-risk, they vary widely in required motor and perceptual skills. The VEP differences among the groups may reflect individual differences in perceptual organization not tapped by written attitudinal scales. A gender effect was present in both VEP components: females showed more of an augmenting response in both thrill-seeking and control groups than the males. However, even when gender was included in the model, no significant differences were found on PlNl between thrill-seeking and control groups. The only significant relationship between VEP and SSS was augmentation with the Dis scale, but this occurred only in the thrill-seeker group for PlNl. This modest correlation (0.29) is consistent with the results of other studies (Zuckerman et al., 1974; Von Knorring, 1981) which also found this relationship with the Dis scale on PlNl but used different VEP procedures. However, Zuckerman’s claim (1984a, p. 417) that a low score on the Dis scale as being associated with a protective cortical mechanism congruent with stimulus avoidance behavior is questionable. The mean Dis scores of the thrill-seekers in this study were relatively low compared to other SSS scores, while by definition, they were not stimulus avoiders. In addition, the results of this study provide no support of an association between VEP and other dimensions of SSS (including Gen), as most of the correlations were near zero. Yet, the only scale to demonstrate reasonable internal consistency reliability was Dis, which may contribute to its being the only significant correlate of VEP. Thrill seekers scored significantly higher than controls on all the SSS scales. These findings are in agreement with other studies of high-risk participants (e.g. Hymbaugh & Garrett, 1974; Bacon, 1974; Kusysyzn et al., 1973; Connolly, 1981; Straub, 1982). It is noteworthy that TAS was the most important scale in differentiating thrill-seekers from controls. This finding provides behavioral evidence in favor of the construct validity of the TAS scale. The robust thrill-seeker scores and discriminating capacity of TAS may indicate that although thrill-seekers usually participate in one specific sport, they have an overall preference for all types of high-risk sports. This can be interpreted as providing support for TAS as an overall personality trait that is manifested in a general desire to engage in many types of high-risk sports. Although thrill-seekers scored significantly higher on all the SSS scales, the lack of significant relationships between TAS and any of the other SSS scales (except Gen) in the thrill-seeking group, and TAS as the primary discriminator between the groups provides evidence for a more specific thrill-seeking trait rather than a broader trait of sensation seeking in thrill-seekers. This is especially true since all SSS subscales are reported to be intercorrelated (Zuckerman, 1979). One can speculate that thrill-seekers as sensation seekers may be attracted to, and specifically channel their need for sensation into, one dimension of sensation seeking: thrill-seeking. The nature of these thrill-seeking activities may provide the high sensations needed for optimal stimulation. Scores on the Gen scale were highly correlated with those on the TAS, ES and BS scales, in both groups, which is consistent with Zuckerman’s et al. (1974, p. 95) findings. The lack of a significant relationship between Dis and Gen scores in the thrill-seeking group may be attributed to the Gen overlapping with only these three scales and not Dis. This lends further support to Zuckerman’s
462
JANET L. BLENNER
(1979) criticism of Gen in SSS form IV as not being a satisfactory measure of overall sensation seeking. The dimensions of the SSS reflect some atypical characteristics of thrill-seekers. The lack of age effects on Gen and TAS scores is different from the effects seen in most SSS studies of the general population (Zuckerman, Eysenck & Eysenck, 1978; Zuckerman, 1979) which report higher thrill-seeking preference in younger males, with a steady decline through adulthood into old age. In this study, interest in TAS was evident even in the older age group. Zuckerman (1984, p. 433) speculated that accessibility for sensation seeking outlets may determine the nature of sensation seeking. His focus was the social class of individuals, and he proposed that the middle class may have more accessibility to sport activities, enabling the members of this class to meet their needs for sensation. All the thrill-seekers in this study were middle class, which supports this contention. In addition, the climate, terrain, and the availability of these types of high-risk activities must be considered. Southern California provides a climate and many different terrains which are supportive of a wide array of thrill-seeking activities all year round. Environmental accessibility coupled with socio-economic class may play significant roles in the channeling of sensation seeking. In conclusion, it is suggested that further research be conducted on the relationship of VEP and SSS using consistent VEP procedures ensuring adequate comparisons of findings. Future thrillseeking studies need to include females and explore the uniqueness of this particular population as related to the sensation seeking construct. Acknowledgemenfs~I would like to acknowledge Drs Monte Buchsbaum and Richard Haier for their editorial suggestions. I would also like to acknowledge Tony Paquin and Judith Rivera for their assistance with data collection and Paul Clopton for his statistical assistance.
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